Atrial fibrillation is an arrhythmia, in which there are unordered excitation pulses from the atria to the ventricles in quick succession. As a result of this, the atria and the ventricles contract independently of one another and at different speeds during the atrial fibrillation. The atria and ventricles are normally stimulated approximately 70 times a minute, directly after one another. In the case of atrial fibrillation there are undirected electrical excitations via the atria, which lead to unordered contractions in quick succession with a frequency of between 350 and 600 times per minute. As a result of this high frequency the atria can no longer pump sufficient blood into the ventricles, which likewise pump less blood into the circulatory system, and so there are variations in the blood pressure.
Atrial fibrillation can be treated by medication. If this is unsuccessful, it is increasingly common to carry out a catheter ablation. In the process, a catheter is advanced into the heart via arterial or venous blood vessels. The catheter is used to sever excitation lines running in the tissue of the cardiac wall of an atrium by means of sclerotherapy of tissue in order to suppress the unordered propagation of excitation pulses. In general, either lesions running in the longitudinal direction are placed in the region of the left atrium or muscle bundles at the openings of the pulmonary veins are ablated in an annular fashion.
The treatment success is often monitored with the aid of CT-angiography (CTA), in which, after a contrast agent is administered, an X-ray computed tomography scanner is used to record X-ray projections of the heart in the patient, which are used to reconstruct slice images of the heart in the patient. In this respect, reference is made in an example fashion to Tops L. F., Schalij M. J., and Bax J. J. “Imaging and atrial fibrillation: the role of multimodality imaging in patient evaluation and management of atrial fibrillation”, European Heart Journal (2010) 31, p. 542-551.
Particularly if the result of the ablation should be assessed on the basis of image information relating to the treated tissue of the atrium of the heart, it is conventional to generate multiplanar reformations (MPR). However, this procedure for visualizing and representing the treated tissue requires the assessing radiologist to have a high degree of experience and knowledge in the art because the cardiac wall is comparatively thin and the differences between normal, untreated tissue and tissue treated within the scope of the ablation are very small.